Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnly=true and destructive=false, so safety is covered; the description adds the substantive behavioral detail that it returns a quota breakdown with used/allowed/left across several resource classes. It does not say whether values are real-time or tied to the current billing period, which is a minor remaining gap.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Three sentences, front-loaded with the use condition, then the return payload, then the routing exclusion. The long return enumeration earns its place because no output schema exists.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema and no parameters, the description carries the burden of describing return values and does so concretely (used/allowed/left, seats, webhooks, retention, fastest interval). An agent has everything needed to call it and interpret the response.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Zero parameters, so the baseline of 4 applies. The description correctly implies no input is needed by framing the tool purely around a question the user asks.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

Specific verb+resource ('Get plan usage and limits') plus an enumeration of exactly what is returned: monitor pool, status pages, seats, webhooks, subscribers, history retention, check interval. It is clearly separable from siblings like list_sites or get_account_overview.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicit trigger conditions ('when the user asks how many monitors they have left, what their plan includes, or why they cannot add more') and an explicit exclusion routing to get_account_overview or list_sites for downtime questions. Both when-to-use and when-not-to-use are covered.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.